有沒有一種簡單的方法將數據添加到Rails中的關係表中？

Question

我有一個菜桌，一個配料表和一個dish_成分表來加入菜餚和配料（見下文）。每次我添加一個配料到菜，我想增加或添加配料的數量dish_ingredient表。我已經設法通過這樣做來更新號碼：

dish.dish_ingredients[counter].number_of_ingredients = new number 

但通過這樣做，我需要管理一個計數器。有沒有簡單的方法在Rails中做到這一點？

class Dish < ActiveRecord::Base 
    has_many :dish_ingredients 
    has_many :ingredients, :through => :dish_ingredients 
end 

class Ingredient < ActiveRecord::Base 
    has_many :dish_ingredients 
    has_many :dishes, :through => :dish_ingredients 
end 

class DishIngredient < ActiveRecord::Base 
    belongs_to :dish 
    belongs_to :ingredient 
end 

# in the database table dish_ingredient contains a field 'number_of_ingredients' 
# that I want to update when ingredients are modified or added to dish. 

Answer 1

你試過

class DishIngredient < ActiveRecord::Base 
    belongs_to :dish 
    belongs_to :ingredient, :counter_cache => true 
end 

？這要求您在dish_ingredient表中具有ingredients_count屬性。 Rails會自動處理更新計數器。

Answer 2

出了什麼問題：

some_dish.ingredients.count